0基础学习Mybatis系列数据库操作框架——Mysql的Geometry数据处理之WKB方案

news/2024/7/27 23:23:05

大纲

  • 序列化
  • 反序列化
  • 完整TypeHandler
  • SQL XML
    • 完整XML
  • Mapper
  • 测试代码
  • 代码

在《0基础学习Mybatis系列数据库操作框架——Mysql的Geometry数据处理之WKT方案》中，我们介绍WTK方案的优点，也感受到它的繁琐和缺陷。比如：

  • 需要借助ST_GeomFromText和ST_AsText，让SQL语句显得复杂。
select id, ST_AsText(geometry) AS geometry, update_time, create_time from geometry_data
  • 没有一种GeomFromText方案可以覆盖所有的Geometry结构，使得类似的SQL要写多份。
insert into geometry_data(id, geometry, update_time, create_time) values(#{id}, ST_GeomFromText(#{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKTHandler}), now(), now())insert into geometry_data(id, geometry, update_time, create_time) values(#{id}, ST_GeomCollFromText(#{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKTHandler}), now(), now())
  • 没有针对LinearRing（一种特殊的LineString）的处理方法。

而本文介绍的WKB方法，则可以解决上述问题。
WKB全程Well-Known Binary，它是一种二进制存储几何信息的方法。
在《0基础学习Mybatis系列数据库操作框架——Mysql的Geometry数据处理之WKT方案》中介绍的WKT方法，可以用字符串形式表达几何信息，如POINT (1 -1)。
WKB则表达为

0101000000000000000000F03F000000000000F0BF

这段二进制的拆解如下

ComponentSizeValue
Byte order1 byte01
WKB type4 bytes01000000
X coordinate8 bytes000000000000F03F
Y coordinate8 bytes000000000000F0BF

byte order可以是0或者1，它表示是大顶堆（0）还是小顶堆（1）存储。
WKB type表示几何类型。值的对应关系如下：

  • 1 Point
  • 2 LineString
  • 3 Polygon
  • 4 MultiPoint
  • 5 MultiLineString
  • 6 MultiPolygon
  • 7 GeometryCollection

剩下的是坐标信息。

虽然这个结构已经很基础，但是**Mysql的Geometry结构并不是WKB。准确的说，WKB只是Mysql的Geometry结构中的一部分。**它们的差异是，Mysql的Geometry结构是在WKB之前加了4个字节，用于存储SRID。
在这里插入图片描述
还有一点需要注意的是，Mysql存储Geometry数据使用的是小顶堆。所以WKB的Byte order字段值一定是1。
有了这些知识，我们就可以定义WKB类型的TypeHandler了。

序列化

这段代码先从org.locationtech.jts.geom.Geometry中获取SRID码；然后以小顶堆模式，使用WKBWriter将几何信息保存为WKB的二进制码。然后申请比WKB大4个字节的空间，分别填入SRID和WKB。这样整个内存结构就匹配Mysql内部的Geometry内存结构了。

    private byte[] serializeGeometry(Geometry geometry) {int srid = geometry.getSRID();byte[] bytes = new WKBWriter(2, ByteOrderValues.LITTLE_ENDIAN).write(geometry);return ByteBuffer.allocate(bytes.length + 4).order(ByteOrder.LITTLE_ENDIAN).putInt(srid).put(bytes).array();}

反序列化

这段代码会将Mysql内部的Geometry内存结构读出来，转换成小顶堆模式。然后获取SRID，并以此创建GeometryFactory。剩下的内容就是WKB的内存了，最后使用WKBReader将这段内存转换成org.locationtech.jts.geom.Geometry。

    private static Geometry deserializeGeometry(byte[] bytes) throws ParseException {if (bytes == null) {return null;}ByteBuffer buffer = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN);int srid = buffer.getInt();byte[] geometryBytes = new byte[buffer.remaining()];buffer.get(geometryBytes);GeometryFactory geometryFactory = GEOMETRY_FACTORIES.computeIfAbsent(srid, i -> new GeometryFactory(PRECISION_MODEL, i));WKBReader reader = new WKBReader(geometryFactory);return reader.read(geometryBytes);}

完整TypeHandler

package org.example.typehandlers;import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.PrecisionModel;
import org.locationtech.jts.io.ByteOrderValues;
import org.locationtech.jts.io.ParseException;
import org.locationtech.jts.io.WKBReader;
import org.locationtech.jts.io.WKBWriter;import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;public class GeometryTypeWKBHandler extends BaseTypeHandler<Geometry>  {private static final PrecisionModel PRECISION_MODEL = new PrecisionModel(PrecisionModel.FIXED);private static final Map<Integer, GeometryFactory> GEOMETRY_FACTORIES = new ConcurrentHashMap<>();@Overridepublic void setNonNullParameter(PreparedStatement ps, int i, Geometry parameter, JdbcType jdbcType) throws SQLException {byte[] bytes = serializeGeometry(parameter);ps.setBytes(i, bytes);}@Overridepublic Geometry getNullableResult(ResultSet rs, String columnName) throws SQLException {byte[] bytes = rs.getBytes(columnName);try {return deserializeGeometry(bytes);} catch (ParseException e) {throw new SQLException(e);}}@Overridepublic Geometry getNullableResult(ResultSet rs, int columnIndex) throws SQLException {byte[] bytes = rs.getBytes(columnIndex);try {return deserializeGeometry(bytes);} catch (ParseException e) {throw new SQLException(e);}}@Overridepublic Geometry getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {byte[] bytes = cs.getBytes(columnIndex);try {return deserializeGeometry(bytes);} catch (ParseException e) {throw new SQLException(e);}}private static Geometry deserializeGeometry(byte[] bytes) throws ParseException {if (bytes == null) {return null;}ByteBuffer buffer = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN);int srid = buffer.getInt();byte[] geometryBytes = new byte[buffer.remaining()];buffer.get(geometryBytes);GeometryFactory geometryFactory = GEOMETRY_FACTORIES.computeIfAbsent(srid, i -> new GeometryFactory(PRECISION_MODEL, i));WKBReader reader = new WKBReader(geometryFactory);return reader.read(geometryBytes);}private byte[] serializeGeometry(Geometry geometry) {int srid = geometry.getSRID();byte[] bytes = new WKBWriter(2, ByteOrderValues.LITTLE_ENDIAN).write(geometry);return ByteBuffer.allocate(bytes.length + 4).order(ByteOrder.LITTLE_ENDIAN).putInt(srid).put(bytes).array();}
}

SQL XML

使用了WKB模式，SQL就会写的很简洁，而不需要用ST_GeomFromText和ST_AsText转来转去。比如之前因为要用ST_AsText处理返回值，导致需要写明每个返回的字段。而使用WKB后，可以写成

    <resultMap id="GeometryDataResultMap" type="org.example.model.GeometryData"><result property="id" column="id"/><result property="geometry" column="geometry" typeHandler="org.example.typehandlers.GeometryTypeWKBHandler" jdbcType="BLOB"/><result property="updateTime" column="update_time"/><result property="createTime" column="create_time"/></resultMap><select id="findAll" resultMap="GeometryDataResultMap">select * from geometry_data</select>

作为对比可以看下WKT的模式，如下。

    <resultMap id="GeometryDataResultMap" type="org.example.model.GeometryData"><result property="id" column="id"/><result property="geometry" column="geometry" typeHandler="org.example.typehandlers.GeometryTypeWKTHandler" jdbcType="BLOB"/><result property="updateTime" column="update_time"/><result property="createTime" column="create_time"/></resultMap><select id="findAll" resultMap="GeometryDataResultMap">select id, ST_AsText(geometry) AS geometry, update_time, create_time from geometry_data</select>

插入操作也会变得简单，下面是WKB模式

    <insert id="insertOne" parameterType="org.example.model.GeometryData"  useGeneratedKeys="true" keyProperty="id">insert into geometry_data(id, geometry, update_time, create_time) values(#{id}, #{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKBHandler}, now(), now())</insert>

而WKT模式，因为不能使用ST_GeomFromText处理GeometryCollection，导致只能拆成两条SQL。如下

    <insert id="insertOne" parameterType="org.example.model.GeometryData"  useGeneratedKeys="true" keyProperty="id">insert into geometry_data(id, geometry, update_time, create_time) values(#{id}, ST_GeomFromText(#{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKTHandler}), now(), now())</insert><insert id="insertGeometryCollection" parameterType="org.example.model.GeometryData"  useGeneratedKeys="true" keyProperty="id">insert into geometry_data(id, geometry, update_time, create_time) values(#{id}, ST_GeomCollFromText(#{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKTHandler}), now(), now())</insert>

可以见得WKB模式让SQL XML变得简单。

完整XML

<?xml version="1.0" encoding="UTF-8"?>
<!-- AllTypeMapper-1.xml -->
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.example.mapper.GeometryDataWKBMapper"><resultMap id="GeometryDataResultMap" type="org.example.model.GeometryData"><result property="id" column="id"/><result property="geometry" column="geometry" typeHandler="org.example.typehandlers.GeometryTypeWKBHandler" jdbcType="BLOB"/><result property="updateTime" column="update_time"/><result property="createTime" column="create_time"/></resultMap><select id="findAll" resultMap="GeometryDataResultMap">select * from geometry_data</select><select id="find" resultMap="GeometryDataResultMap">select * from geometry_data where id = #{id}</select><insert id="insertOne" parameterType="org.example.model.GeometryData"  useGeneratedKeys="true" keyProperty="id">insert into geometry_data(id, geometry, update_time, create_time) values(#{id}, #{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKBHandler}, now(), now())</insert><insert id="insertList" parameterType="list">insert into geometry_data(id, geometry, update_time, create_time) values<foreach item="item" collection="list" separator=",">(#{item.id}, #{item.geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKBHandler}, now(), now())</foreach></insert><update id="updateOne" parameterType="org.example.model.GeometryData">update geometry_data set geometry = #{geometry, jdbcType=BLOB, typeHandler=org.example.typehandlers.GeometryTypeWKBHandler}, update_time = now() where id = #{id} </update>
</mapper>

Mapper

package org.example.mapper;import java.util.List;import org.example.model.GeometryData;public interface GeometryDataWKBMapper {public List<GeometryData> findAll();public GeometryData find(Long id);public Long insertOne(GeometryData geometryData);public Long insertList(List<GeometryData> geometryDataList);public Long updateOne(GeometryData geometryData);
}

测试代码

相较于WKT模式，我们给WKB模式的测试用例增加了LinearRing类型。这是WKT模式所不支持的。

package org.example;import static org.junit.jupiter.api.Assertions.fail;import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.example.mapper.GeometryDataWKBMapper;
import org.example.model.GeometryData;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryCollection;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.geom.LineString;
import org.locationtech.jts.geom.LinearRing;
import org.locationtech.jts.geom.MultiLineString;
import org.locationtech.jts.geom.MultiPoint;
import org.locationtech.jts.geom.MultiPolygon;
import org.locationtech.jts.geom.Polygon;public class GeometryDataWKBTest {private static SqlSessionFactory sqlSF;@BeforeAllstatic void CreateSessionFactory() throws IOException {InputStream in = Resources.getResourceAsStream("mybatis/config/mybatis-config-geometry-wkb.xml");sqlSF = new SqlSessionFactoryBuilder().build(in);}@Testpublic void testFindAll() {List<GeometryData> all = null;try (SqlSession session = sqlSF.openSession()) {all = session.getMapper(GeometryDataWKBMapper.class).findAll();} catch (Exception e) {System.out.println(e.getMessage());}for (GeometryData a : Objects.requireNonNull(all)) {System.out.println(a.getGeometry());}}@Testpublic void testFind() {try (SqlSession session = sqlSF.openSession()) {GeometryDataWKBMapper GeometryDataWKBMapper = session.getMapper(GeometryDataWKBMapper.class);GeometryData one = GeometryDataWKBMapper.find(1L);System.out.println(one.getGeometry());} catch (Exception e) {System.out.println(e.getMessage());}}@Testpublic void testInsert() {try (SqlSession session = sqlSF.openSession()) {GeometryDataWKBMapper GeometryDataWKBMapper = session.getMapper(GeometryDataWKBMapper.class);GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();Coordinate coordinate = new Coordinate(1, 1);Geometry geometry = geometryFactory.createPoint(coordinate);geometryData.setGeometry(geometry);long count = GeometryDataWKBMapper.insertOne(geometryData);System.out.println(count);session.commit();} catch (Exception e) {System.out.println(e.getMessage());fail();}}@Testpublic void testUpdate() {try (SqlSession session = sqlSF.openSession()) {GeometryDataWKBMapper GeometryDataWKBMapper = session.getMapper(GeometryDataWKBMapper.class);GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();Coordinate coordinate = new Coordinate(2, 2);Geometry geometry = geometryFactory.createPoint(coordinate);geometryData.setId(1L);geometryData.setGeometry(geometry);long count = GeometryDataWKBMapper.updateOne(geometryData);System.out.println(count);session.commit();} catch (Exception e) {System.out.println(e.getMessage());fail();}}@Testpublic void testInsertList() {try (SqlSession session = sqlSF.openSession()) {GeometryDataWKBMapper GeometryDataWKBMapper = session.getMapper(GeometryDataWKBMapper.class);List<GeometryData> geometryDataList = new ArrayList<>();{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();Coordinate coordinate = new Coordinate(3, 3);Geometry geometry = geometryFactory.createPoint(coordinate);geometryData.setGeometry(geometry);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();LineString lineString = geometryFactory.createLineString(new Coordinate[] { new Coordinate(1, 1), new Coordinate(2, 2) });geometryData.setGeometry(lineString);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();MultiLineString multiLineString = geometryFactory.createMultiLineString(new LineString[] {geometryFactory.createLineString(new Coordinate[] { new Coordinate(1, 1), new Coordinate(2, 2) }),geometryFactory.createLineString(new Coordinate[] { new Coordinate(3, 3), new Coordinate(4, 4) })});geometryData.setGeometry(multiLineString);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();MultiPolygon multiPolygon = geometryFactory.createMultiPolygon(new Polygon[] {geometryFactory.createPolygon(new Coordinate[] { new Coordinate(1, 1), new Coordinate(2, 2),new Coordinate(3, 3), new Coordinate(1, 1) }),geometryFactory.createPolygon(new Coordinate[] { new Coordinate(4, 4), new Coordinate(5, 5),new Coordinate(6, 6), new Coordinate(4, 4) })});geometryData.setGeometry(multiPolygon);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();LinearRing linearRing = geometryFactory.createLinearRing(new Coordinate[] { new Coordinate(1, 1),new Coordinate(2, 2), new Coordinate(3, 3), new Coordinate(1, 1) });geometryData.setGeometry(linearRing);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();MultiPoint multiPoint = geometryFactory.createMultiPointFromCoords(new Coordinate[] { new Coordinate(1, 1), new Coordinate(2, 2), new Coordinate(3, 3) });geometryData.setGeometry(multiPoint);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();Polygon polygon = geometryFactory.createPolygon(new Coordinate[] { new Coordinate(1, 1),new Coordinate(2, 2), new Coordinate(3, 3), new Coordinate(1, 1) });geometryData.setGeometry(polygon);geometryDataList.add(geometryData);}{GeometryData geometryData = new GeometryData();GeometryFactory geometryFactory = new GeometryFactory();GeometryCollection geometryCollection = geometryFactory.createGeometryCollection(new Geometry[] {geometryFactory.createPoint(new Coordinate(1, 1)),geometryFactory.createLineString(new Coordinate[] { new Coordinate(1, 1), new Coordinate(2, 2) }),geometryFactory.createPolygon(new Coordinate[] { new Coordinate(1, 1), new Coordinate(2, 2),new Coordinate(3, 3), new Coordinate(1, 1) })});geometryData.setGeometry(geometryCollection);geometryDataList.add(geometryData);}long count = GeometryDataWKBMapper.insertList(geometryDataList);System.out.println(count);session.commit();} catch (Exception e) {System.out.println(e.getMessage());fail();}}
}

在这里插入图片描述

代码

https://github.com/f304646673/mybatis_demo

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